In recent years, transistors using organic materials (organic semiconductor materials) possessing electrically conductive properties similar to semiconductors have been under development. The transistors have advantages of good adaptability to low-profile and weight-saving, flexibility, low material cost and so on. Transistors can be used to realize switching elements for flexible displays or the like.
To realize switching elements, a structure for transistors is proposed in which a source electrode and a drain electrode are formed on a substrate with an organic semiconductor layer, a gate insulating layer, and a gate electrode stacked, respectively.
Japanese Unexamined Patent Publication No. 5-55568 discloses that a vacuum deposition method is used for forming a gate electrode, a source electrode, and a drain electrode.
By forming an insulating layer and an organic semiconductor layer using the vacuum deposition method in addition to forming the gate electrode, the source electrode, and the drain electrode using the vacuum deposition method as described in Japanese Unexamined Patent Publication No. 5-55568, a high-performance transistor can be manufactured with good reproducibility.
However, the vacuum deposition method requires a large-scale facility, and can present problems of high-cost and so on resulting from large power consumption required to form the films.
International Patent Publication Nos. WO/0147045 and WO/0147043 disclose that the gate electrode, the source electrode, drain electrode, the insulating layer, and the organic semiconductor layer are formed as films by a wet process under atmospheric pressure. As such, a transistor can be manufactured at low cost.
However, in practice, the transistors described in International Patent Publication Nos. WO/0147045 and WO/0147043 do not possess the properties which lead to high performance and good reproducibility when compared with transistors manufactured by the vacuum deposition process.
Aspects of the present invention provide a method of manufacturing a high performance transistor using a relatively simple process, and a transistor circuit equipped with a transistor manufactured according to aspects of the present invention.
A method of manufacturing a transistor according to the present invention comprises: (a) attaching a charge control agent to a first region of a substrate; (b) irradiating a part of the first region with light; (c) selectively attaching a catalytic agent or a precursor of the catalytic agent to the irradiated part of the first region or the first region; (d) depositing a metallic layer from a metallic salt solution on the area attached with one of the catalytic agent and the precursor of the catalytic agent to form one or more electrodes; and (e) forming a semiconductor layer on the electrodes directly or via an insulation layer.
According to one aspect of the present invention, in the method of manufacturing a transistor, the charge control agent is an organic charge control agent; in step (a), the organic charge control agent is attached so as to obtain a substantially even first charging condition in the first region; and in step (b), the charging condition of the irradiated area irradiated with the light is changed to a condition different from the first charging condition by the irradiation with the light.
Further, in step (b), irradiation with the light can be performed so as to decompose the charge control agent. Further, the light can be vacuum ultraviolet radiation.
Still further, in the above manufacturing method, the charge control agent can be a surfactant. In this case, the surfactant is preferably a cationic surfactant.
Further, in one aspect, the catalytic agent or the precursor of the catalytic agent can include palladium.
Further, in the method of manufacturing a transistor according to one aspect of the present invention, the difference between the first charging condition and the charging condition of the irradiated area is greater than or equal to 10 mV in zeta potential in water. The difference is preferably greater than or equal to 30 mV.
In a further aspect, the metallic layer can include at least one metal of Pt, Pd, Ni, Cu, and Au.
Further, in the method of manufacturing a transistor according to another aspect of the present invention, the semiconductor layer can comprise an organic semiconductor. Further, the organic semiconductor can be obtained by coating a solution. Still further, the organic semiconductor can be a conjugated polymer.
Further, in the method of manufacturing a transistor according to another aspect of the present invention, the electrodes described above can be a source electrode and a drain electrode. Still further, the method can comprise (f) forming a gate electrode by applying a coating of one of a solution and a dispersion fluid of an electrically conductive material to overlap a region between the source electrode and the drain electrode. And, the coating of one of the solution and the dispersion fluid of the electrically conductive material can be applied using an inkjet coating process.
Alternatively, the method can comprise prior to step (a): (g) forming a gate electrode; and (h) forming an insulation layer on the gate electrode, wherein the source electrode and the drain electrode are formed on the insulation layer.
Further, according to an aspect of the present invention, a method of manufacturing an electro-optical device equipped with a substrate for holding an electro-optical material, comprises: (a) attaching a charge control agent to a first region of the substrate; (b) irradiating a part of the first region with light; (c) selectively attaching a catalytic agent or a precursor of the catalytic agent to the irradiated part of the first region or the first region; (d) depositing a metallic layer from a metallic salt solution on the area attached with one of the catalytic agent and the precursor of the catalytic agent to form one or more electrodes; and (e) forming a semiconductor layer on the electrodes directly or via an insulation layer.
Further, a transistor according to an aspect of the present invention can be manufactured by the method of manufacturing a transistor described above.
Further, an electro-optical device according to the present invention can be equipped with a transistor manufactured by the method of manufacturing a transistor described above.
According to the aforementioned present invention, a transistor and a transistor circuit can be formed with less waste of materials, low cost, and high precision.